Isotope Abundance

Magnesium consists of three naturally occurring isotopes. The percent abundance of  these isotopes is as follows: ²⁴Mg (78.70%), ²⁵Mg (10.13%), and ²⁶Mg (11.7%). The average atomic mass of the three isotopes is 24.3050 amu. If the atomic mass of ²⁵Mg is 24.98584 amu, and ²⁶Mg is 25.98259 amu, calculate the actual atomic mass of ²⁴Mg.  

• 23.985 amu
• 21.421 amu
• 24.463 amu
• 24.002 amu

 Copper occurs naturally as Cu-63 and Cu-65. Which isotope is more abundant?

• Cu-63
• Cu-65

The atomic masses and the relative abundances of 2 naturally occurring isotopes of an unknown element X are as following: isotope X-7 has a relative abundance of 95% and isotope X-10 has a relative abundance of 5%. Which of the following is correct

• (7 x 95) + (10 x 5)
• (7 x 0.95) + (10 x 0.05)
• (7 x 0.95) + (10 x 0.5)
• (0.7 x 95) + (0.10 x 5)

How many protons does this isotope of titanium have?

• 48
• 22
• 26
• 70

How many neutrons does the isotope of lithium have?

• 8
• 3
• 4
• 5

Tags

NGSS.HS-PS1-8

In a correctly written symbol what would be located in the "A" position?

• number of neutrons
• atomic number
• number of electrons 
• mass number

What quantities vary between isotopes of an element?

• protons, electrons, and atomic mass
• protons, electrons, and atomic number
• neutrons and electrons
• neutrons and atomic mass

Tags

NGSS.HS-PS1-8

Four isotopes of lead include lead-204, lead-206, lead-207, and lead-208.  The average atomic mass of lead is 207.2.  Which isotope of lead is likely to be the most abundant.

• 204
• 206
• 207
• 208

What is an isotope? 

• A charged atom
• An atom with different amounts of neutrons
• An atom with different amounts of protons
• A neutral atom

Calculate the average atomic mass of element X when 34% of element X exists as X-272 and the remainder exists as X-274.

• 185.64amu
• 273.32amu
• 272.68amu
• 27.33amu